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One of the HVAC contractors that spec'ed Central AC, told me I should put 1 AH in the attic and wanted to use Carrier Infiniti FE4A (4 ton unit) for the entire house. He said you can make 2 zones with this unit.

Does this sound right? Would 2 seperate AH's be better?

He was the HVAC contractor I trusted the most because he sounded like he know alot. I use the word sounded, because I am not a HVAC expert by any means but he spoke like he knew what he was talking about. He was also the most expensive, but not by much.

Infinty zoning is probably one of the best systems out there. Its' modulating and you could even zone each bedroom space and also zone the basement as well as different parts of the downstairs if the useage or occupany varies. I question if you need 4 tons, especially if zoned. I bet with spray foam throguhout a load calculation will say 3 tons is plenty. You're only in Queens, not South Florida or Texas. You summer design temeprature isn't that high and humidity is moderate. WIth zoning you can actually undersize slightly and take advantage of even longer run times since all zones are rarely occupied during peak periods.

However, with zoning, ductwork sizing and layout is even more critical.

One of the HVAC contractors that spec'ed Central AC, told me I should put 1 AH in the attic and wanted to use Carrier Infiniti FE4A (4 ton unit) for the entire house. He said you can make 2 zones with this unit.

Does this sound right? Would 2 seperate AH's be better?

He was the HVAC contractor I trusted the most because he sounded like he know alot. I use the word sounded, because I am not a HVAC expert by any means but he spoke like he knew what he was talking about. He was also the most expensive, but not by much.

Good system. Tonnage is at the high end of good, you'll get alot of different opinions that, but 500sqft per ton is ok. A 3 or 3 1/2 ton will work with better dehumidification but on a 95 degree day may not shut off and struggle to maintain set point. If you are planning to use and condition the basement I would stick with 4 tons, won't need much cooling down there but may add to much for the 3 or 3 1/2 ton.

Good system. Tonnage is at the high end of good, you'll get alot of different opinions that, but 500sqft per ton is ok. A 3 or 3 1/2 ton will work with better dehumidification but on a 95 degree day may not shut off and struggle to maintain set point. If you are planning to use and condition the basement I would stick with 4 tons, won't need much cooling down there but may add to much for the 3 or 3 1/2 ton.

I disagree. A below grade basement without a lot of windows, that's not occupied, will acutally have a negative heat load. In a zoned system, I'd even treat it as a heat sink. It will rarely if ever be calling for cooling unless you're entertaining.

IF well insulation, 2000 sqft townhome in that climate might only really need 2-2/12 tons. 3 will be plenty and even if the load cal says 3.2 or 3.5 tons, with a zone system, you can undersize.

A 95F day is 6-7F above design temprature there. where you might need 3.5-4 tons for Missouri, Texas or Florida, you'd only need 3 tons in Queens.

Plus on zoning, oversizeing causes problems, because now you need even larger ducts and more supplies for the smallest zone. Infinity, helps with this by modulating, but you can still find that other zones are over conditioned. Of course a proper Manual D and room by room load calculation will eliminate all of these problems.

I disagree. A below grade basement without a lot of windows, that's not occupied, will acutally have a negative heat load. In a zoned system, I'd even treat it as a heat sink. It will rarely if ever be calling for cooling unless you're entertaining.

IF well insulation, 2000 sqft townhome in that climate might only really need 2-2/12 tons. 3 will be plenty and even if the load cal says 3.2 or 3.5 tons, with a zone system, you can undersize.

A 95F day is 6-7F above design temprature there. where you might need 3.5-4 tons for Missouri, Texas or Florida, you'd only need 3 tons in Queens.

Plus on zoning, oversizeing causes problems, because now you need even larger ducts and more supplies for the smallest zone. Infinity, helps with this by modulating, but you can still find that other zones are over conditioned. Of course a proper Manual D and room by room load calculation will eliminate all of these problems.

Although temperatures aren't that high here in NYC, the humidity kills. Don't know if that affects the tonnage or not.

I should add that my cellar (7.5' ceilings) is fully finished and will be occupied alot. We have the main TV area there and an entrance to the outside. Although, it stays pretty cool compared to the rest of the house and this is pre-renovation, and we will insulate it even better during construction.

I think I am leaning towards a central zoned Infiniti system. I will double check with the HVAC contractor about the tonnage.

Other contractors who did not recommend the Infiniti (actually talked bad about it, being a waste of money) wanted to put 2 AH units, 1 3 ton for cellar and main floor and 1 2 ton for bedrooms.

Although temperatures aren't that high here in NYC, the humidity kills. Don't know if that affects the tonnage or not.

I should add that my cellar (7.5' ceilings) is fully finished and will be occupied alot. We have the main TV area there and an entrance to the outside. Although, it stays pretty cool compared to the rest of the house and this is pre-renovation, and we will insulate it even better during construction.

I think I am leaning towards a central zoned Infiniti system. I will double check with the HVAC contractor about the tonnage.

Other contractors who did not recommend the Infiniti (actually talked bad about it, being a waste of money) wanted to put 2 AH units, 1 3 ton for cellar and main floor and 1 2 ton for bedrooms.

THe design dewpoint is fairly high considering the moderate dry bulb design temperature. Its 'a 73F Dewpoint. But still not as high as 75-77F in more humid parts of the contry. That does affect your load, but I think you still wouldn't need 4 tons in that space unless air leakage is very high . Being new construction, it should be fairly good. Plus, if humidity is the concern, then yet again, oversizing will only make it worse. You don't want it be in low stage 90% of the time where you have a lower latent ratio. Properly sized, you'd should be in low stage around maybe 2/3rds of the run time through the whole season.

THe design dewpoint is fairly high considering the moderate dry bulb design temperature. Its 'a 73F Dewpoint. But still not as high as 75-77F in more humid parts of the contry. That does affect your load, but I think you still wouldn't need 4 tons in that space unless air leakage is very high . Being new construction, it should be fairly good. Plus, if humidity is the concern, then yet again, oversizing will only make it worse. You don't want it be in low stage 90% of the time where you have a lower latent ratio. Properly sized, you'd should be in low stage around maybe 2/3rds of the run time through the whole season.

Thanks for the insight. I will ask him what he feels about going with a 3.5 ton unit.

If cost isnt too much of a factor look into vrf (variable refrigerant flow) mini splits daikan, mitsubishi, Samsung, johnson controls all make them. They are super efficient and quiet. You can have ducted and ductless indoor units and on some models. These types of units are where the hvac industry is headed IMO, especially in urban areas where space is limited. Good luck and know that you can put the most efficient, cutting edge top dollar piece of eqipment in but if it is not sized and installed properly you will have problems, so choose a good contractor to work with

Agree with this post... including get a competent contractor (actually the competent contractor is the MOST important part). Drains for each mini head (part you see in each room) is important also.
The multi-head systems have come a LONG way in recent years; they are quiet and comfortable.

I would shop lots of contractors installing Daiken and Mitsubishi. Fujitsu is a good co, however lately they are having issues.

I disagree. A below grade basement without a lot of windows, that's not occupied, will acutally have a negative heat load. In a zoned system, I'd even treat it as a heat sink. It will rarely if ever be calling for cooling unless you're entertaining.

IF well insulation, 2000 sqft townhome in that climate might only really need 2-2/12 tons. 3 will be plenty and even if the load cal says 3.2 or 3.5 tons, with a zone system, you can undersize.

A 95F day is 6-7F above design temprature there. where you might need 3.5-4 tons for Missouri, Texas or Florida, you'd only need 3 tons in Queens.

Plus on zoning, oversizeing causes problems, because now you need even larger ducts and more supplies for the smallest zone. Infinity, helps with this by modulating, but you can still find that other zones are over conditioned. Of course a proper Manual D and room by room load calculation will eliminate all of these problems.

Make sure the contractor you choose is geared to do residental.Most of the folks in Queens dabble very lightly in residental and are truly commercial companies that are slow and need something to fill the time.I used to see it all the time.Then they do the job and screw the homeowner then dissappear.

I disagree. A below grade basement without a lot of windows, that's not occupied, will acutally have a negative heat load. In a zoned system, I'd even treat it as a heat sink. It will rarely if ever be calling for cooling unless you're entertaining.

IF well insulation, 2000 sqft townhome in that climate might only really need 2-2/12 tons. 3 will be plenty and even if the load cal says 3.2 or 3.5 tons, with a zone system, you can undersize.

A 95F day is 6-7F above design temprature there. where you might need 3.5-4 tons for Missouri, Texas or Florida, you'd only need 3 tons in Queens.

Plus on zoning, oversizeing causes problems, because now you need even larger ducts and more supplies for the smallest zone. Infinity, helps with this by modulating, but you can still find that other zones are over conditioned. Of course a proper Manual D and room by room load calculation will eliminate all of these problems.

Moto is not wrong just has a different opinion on sizing. Well I wouldn't even say different my opinion was 4 ton was that it was on the high end of good. I tend to stay just above optimal for only one reason. PR. While a 3-3 1/2 will do the job 95% of the time 5% of the time, at least in my neck of the woods, it would struggle to maintain set point. That's the only time most customers would think about "that guy" that sold them that system. And "that guy" sold them something that can't cool their house. In my experience " it's doing all it can" is not what they want to hear on a 95-100 degree day or when the whole family is over for a birthday party and all zones are calling and the every burner on the stove and oven are on. Absolutely the 3-3 1/2 will give better dehumidification but will give up cooling under heavy load a bit more. Now knowing and understanding that you agin are the deciding factor. Agin 6 of one half dozen of the other. Both options are correct. One is more correct for you. Good luck.

That's a matter of managing perceptions. Just tell them that it running continusly is saving them money. Oversizing can cut system efficiency by as much at 30% because of short cycles. Its' just like driving your car on short trips and the engine cooling off each time you stop vs a long continous trips. My commute each day is a 5 miles round trip to work... plus a 1/2 mile walk from the parking lot to my office. My fuel economy is pretty low, around 15-19mpg depending on how hot or cold it is outside. But it increased by about 30% when we moved last year and I started parking in a semi-conditioned garage.

I guess my point on this thread, is that unitl a load calculation is done, we don't know for sure what the sizing is. But I think it could easily come out at 3 Tons or smaller. Shading and type of insulation used will make a big difference.

One more thought. "Struggling" to maintain set point. I think as an industry, need to decribe that a better way. My upstairs unit at home is sized perfectly. It "struggled" all summer long and even fell behind 1-2F on the hottest days. But that was when it was 8-10F above design temperatures. It ran sometimes for 12-14 hours straight, about 1/2 of that time in 2nd stage, the other 1/2 in first stage. No setbacks. It actually would have fallen behind more, but I keep the blinds shut on the hottest days. Humidity stays at a nice 48-50% and drops to 42-45% by late evening. Going up a size to a 3 ton, would have allowed it to maintain temp on thsoe days, but at the cost of higher humidty the other 95% of the time, and higher energy use from short cycling in cooler days. Plus it would be noiser and static pressure would be higher. Actually, I'd lose almost 0.5 SEER just from thigher static pressure.

That's a matter of managing perceptions. Just tell them that it running continusly is saving them money. Oversizing can cut system efficiency by as much at 30% because of short cycles. Its' just like driving your car on short trips and the engine cooling off each time you stop vs a long continous trips. My commute each day is a 5 miles round trip to work... plus a 1/2 mile walk from the parking lot to my office. My fuel economy is pretty low, around 15-19mpg depending on how hot or cold it is outside. But it increased by about 30% when we moved last year and I started parking in a semi-conditioned garage.

I guess my point on this thread, is that unitl a load calculation is done, we don't know for sure what the sizing is. But I think it could easily come out at 3 Tons or smaller. Shading and type of insulation used will make a big difference.

One more thought. "Struggling" to maintain set point. I think as an industry, need to decribe that a better way. My upstairs unit at home is sized perfectly. It "struggled" all summer long and even fell behind 1-2F on the hottest days. But that was when it was 8-10F above design temperatures. It ran sometimes for 12-14 hours straight, about 1/2 of that time in 2nd stage, the other 1/2 in first stage. No setbacks. It actually would have fallen behind more, but I keep the blinds shut on the hottest days. Humidity stays at a nice 48-50% and drops to 42-45% by late evening. Going up a size to a 3 ton, would have allowed it to maintain temp on thsoe days, but at the cost of higher humidty the other 95% of the time, and higher energy use from short cycling in cooler days. Plus it would be noiser and static pressure would be higher. Actually, I'd lose almost 0.5 SEER just from thigher static pressure.

Agin I'm not disagreeing. You and I are in agreement. However you and I understand what you are saying and expect to give up 1-2 degree on those above design days. Jonny homeowner usually doesn't. At least not until they are billed $100 or more an hour for someone like yourself or me to come out and explain it to them. All they know is they spent x thousands of dollars for a new AC system they set their T stat at 74 but its 76-77 and it's been running all day. OP was quoated a 4 ton zoned system by an HVAC contractor who apparently came out and looked at it. Another contractor quoated 2 systems at 4 1/2 total tons. I don't know if they did a load calc on it but they at least saw it. Neither of us have so we really can't disagree about what he needs cause we really don't know. But I believe we have both given, along with many others, very good information to help him make an informed decision about what works for him.

[QUOTE=Tommy knocker;14193411] OP was quoated a 4 ton zoned system by an HVAC contractor who apparently came out and looked at it. Another contractor quoated 2 systems at 4 1/2 total tons. I don't know if they did a load calc on it but they at least saw it. QUOTE]

They quoted me based off the architectual drawings and the assumption I will be spray foaming everything (The drawings called for R18 or higher)